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Thread: Resolution issues

  1. #1

    Default Resolution issues

    Dear Guys,

    3 questions here:

    1. My D70 is a 6mb camera. So if i use the biggest format to shoot, which is RAW, the biggest file i can get is should not be more than 6 mb right?

    2. Based on calculation, for a 6mb photo, the biggest print i can go, at 200dpi, should be super 10R right? [(2000 by 3000) multiply by 200 dpi = 6 million pixel, ie, 6mb]

    3. On the same batch of photos, how come some of them are shown as 72 in resolution while some are at 180 and the most at 300?

    Thank u for taking time to reply guys

  2. #2

    Default Re: Resolution issues

    6 Megapixels.. Not 6 mb camera!

  3. #3
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    Default Re: Resolution issues

    Quote Originally Posted by iltriumph View Post
    Dear Guys,

    3 questions here:

    1. My D70 is a 6mb camera. So if i use the biggest format to shoot, which is RAW, the biggest file i can get is should not be more than 6 mb right?

    2. Based on calculation, for a 6mb photo, the biggest print i can go, at 200dpi, should be super 10R right? [(2000 by 3000) multiply by 200 dpi = 6 million pixel, ie, 6mb]

    3. On the same batch of photos, how come some of them are shown as 72 in resolution while some are at 180 and the most at 300?

    Thank u for taking time to reply guys
    1. D70 is a 6MP camera... not 6MB... 2ndly yes d70 raw is about 5MB+/- in size.

    2. probably bigger than S10R when PP is done correctly... do you think ppl use 10000MP to print billboard?

    3. most probably user error when saving the photos after processing...

  4. #4

    Default Re: Resolution issues

    1. Camera sensor "resolution" is measured in pixel counts, eg 6 megapixels and NOT 6 MB. The pixel count is an indication of how "accurately" it can capture reality.

    (You must realised that some parts of reality are inevitably lost in any digitisation process. The question is whether the parts thrown away are relevant or significant which is something you may never know.)

    2. The captured image file size depends on many factors, a main one being the number of bits used to represent the information each pixel captures. So if 8 bits or 1 byte is used than at most your image is 6 MB (6 megapixels x 1 byte/pixel). But usually it is less than that as the data stored is compressed. In RAW and TIFF this compression is lossless. RAW files are in fact smaller than TIFF files. Also some sensors have more than 8 bits per pixels, maybe something like 12 bits.

    3. A Super 10R print is 15"x10", which at 200dpi, means your picture will be represented as 3000 x 2000 = 6 megapixel picture = 6 MB (if it is 1 byte/pixel). However note that you can represent each pixel by more than 1 byte. For example in Photoshop you can processed your pictures represented in 16 bits/pixel. There are some reasons for doing this. But of course when you talk about printing, then it depends on what your printer can take, which is usually 1 byte/pixel, I think.

    4. I dont understand what you mean by "on some batch of photos".

    5. But I think the context from which you are asking, "resolution" is something like a scale, to generate the physical size of the area to represent your image data. No data is lost or created by changing the resolution. For example if you have a 3000 x 2000 pixel image data, then if you set the "scale" or "resolution" to 72 dpi, then your full picture will be displayed on an area 3000/72 x 2000/72 = 42" x 28" area. But if you set it to 300 dpi, then it will be displayed in an area 10"x6.7".

    The reason for confusion is that the same word, resolution, is used to measure two different concepts, namely, image content and media display characteristics. The former is informational while the latter is physical. A high resolution image means a lot of image content, whereas the resolution of the display media - be it CRT, LCD, paper - determines the physical size of the image when displayed.
    Last edited by espion; 7th March 2007 at 11:30 PM.

  5. #5
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    Default Re: Resolution issues

    You are right in your calculation below....but do you need 200dpi or not is a question lah....like if you meant to view the pic far away, the dpi can be less, thus bigger print.

    Quote Originally Posted by iltriumph View Post

    2. Based on calculation, for a 6mb photo, the biggest print i can go, at 200dpi, should be super 10R right? [(2000 by 3000) multiply by 200 dpi = 6 million pixel, ie, 6mb]

  6. #6
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    Default Re: Resolution issues

    Quote Originally Posted by iltriumph View Post
    Dear Guys,

    3 questions here:

    1. My D70 is a 6mb camera. So if i use the biggest format to shoot, which is RAW, the biggest file i can get is should not be more than 6 mb right?

    2. Based on calculation, for a 6mb photo, the biggest print i can go, at 200dpi, should be super 10R right? [(2000 by 3000) multiply by 200 dpi = 6 million pixel, ie, 6mb]

    3. On the same batch of photos, how come some of them are shown as 72 in resolution while some are at 180 and the most at 300?

    Thank u for taking time to reply guys
    1) like others have said... photo size does not relate to file size... although in raw the file size will be close to the number of megapixels.. like for ur case around 5-6+/- MB... but seriously does it matter? go take a few photos and find out urself.. u'll get files of different sizes but all within a certain range...
    raw in itself is a compressed format... try to convert one of ur files to 16 bit tiff and u'll get what i mean.. ur photo will be 30-40MB...

    2) this is not necessarily true.. u have to find out if ur camera produces images in the same ratio as the photos... if not u may not be able to maximise the use of hte entire photo, and might end up printing smaller..

    for eg., if u have a photo that is not the same ratio, u have to crop it so that it fits the photo paper.. u would have lost pixels then... so at the same dpi u will have to print on a smaller piece of paper...

    3) most cameras produce images at 72dpi.. coz that's what most screens will display them as.. but it's always interchangeable.. the resolution is not important, as long as all the pixels are there.. u can send a photo to a printing studio at 72 dpi and they'll change the resolution accordingly to fit the quality required from u....
    Last edited by Adelfin; 8th March 2007 at 10:43 AM.
    Canon EOS 30D w/ grip 580EX, Tamron 28-75mm f/2.8, EF-S 10-22mm
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  7. #7
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    Default Re: Resolution issues

    2000 by 3000 pixels

    @ 300dpi = 6.6" x 10"
    @ 200dpi = 10" x 15"
    @ 100dpi = 20" x 30"

  8. #8

    Default Re: Resolution issues

    Hey Guys,

    Thank u for your kind and detailed replies.

    For large prints, say 2m by 3m what is the lowest dpi that we can go without losing much quality (assuming picture being viewed within 3m) ?

    Thanks

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    Default Re: Resolution issues

    Quote Originally Posted by iltriumph View Post
    Hey Guys,

    Thank u for your kind and detailed replies.

    For large prints, say 2m by 3m what is the lowest dpi that we can go without losing much quality (assuming picture being viewed within 3m) ?

    Thanks
    it depends.. if u can afford the pixels i'd say go for 300dpi... but for that u may have to stitch ur photos together....

    the lowest i'd ever go is prob about 150dpi.... if viewed a little further away u could afford 100dpi or 72 dpi... because the photo will be big, chances are people will stand back and view the big picture, rather then go close and scrutinise the pimples on someone's face... so a high resolution may not be that impt...
    Canon EOS 30D w/ grip 580EX, Tamron 28-75mm f/2.8, EF-S 10-22mm
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  10. #10

    Default Re: Resolution issues

    The formula is: ppi = 1/((distance x 0.000291) / 2)*.

    So 3m viewing, ie about 10ftx12" = 120", the ppi = 1/(120x0.000291)/2 = 57 dpi. So I suppose 100 dpi is safe enough.

    See here for more.

    * These numbers, I think, are derived from the size of our rods in our retina itself, our natural imaging sensing "pixels" in our eyes.
    Last edited by espion; 9th March 2007 at 10:17 AM.

  11. #11
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    Default Re: Resolution issues

    Yah, it all are derived from the ability of our eyes to differential 2 dots/lines from a distance.....it all started with 5lines/mm at 25cm viewing distant. It is how COC for lens is calculated....

    Quote Originally Posted by espion View Post
    The formula is: ppi = 1/((distance x 0.000291) / 2)*.

    So 3m viewing, ie about 10ftx12" = 120", the ppi = 1/(120x0.000291)/2 = 57 dpi. So I suppose 100 dpi is safe enough.

    See here for more.

    * These numbers, I think, are derived from the size of our rods in our retina itself, our natural imaging sensing "pixels" in our eyes.

  12. #12
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    Default Re: Resolution issues

    Quote Originally Posted by espion View Post
    The formula is: ppi = 1/((distance x 0.000291) / 2)*.

    So 3m viewing, ie about 10ftx12" = 120", the ppi = 1/(120x0.000291)/2 = 57 dpi. So I suppose 100 dpi is safe enough.

    See here for more.

    * These numbers, I think, are derived from the size of our rods in our retina itself, our natural imaging sensing "pixels" in our eyes.
    haha even at 60DPI, you will need about 34MP...

  13. #13

    Default Re: Resolution issues

    ok, thank u all for the inputs.

    Cheers!

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